1. Field of the Invention
The present invention relates to improvements in a temperature control device and temperature control method comprising a fluid circulating and supplying system for circulating and supplying a thermal fluid adjusted to a prescribed set temperature to an object whose temperature is to be controlled, which controls a temperature of the object whose temperature is to be controlled by means of the thermal fluid supplied by the fluid circulating and supplying system.
2. Description of the Related Art
A thermal fluid, such as air supplied to a thermostatic chamber, or a thermal fluid, such as water or FLUORINART (registered trademark) used in controlling the air conditions or side wall temperature of a chamber employed in the manufacture of semiconductor devices, liquid crystal devices, or the like, must be controlled to a target temperature according to its respective object. Therefore, in a semiconductor manufacturing system, for example, a circulating and supplying system for the thermal fluid is adopted, whereby the thermal fluid used for temperature control of the chamber is caused to flow into a heat exchanger, such as a heater, chiller, or the like, the thermal fluid is adjusted to a desired temperature in the heat exchanger, and the thermal fluid is then supplied to the chamber.
Prior art of this kind is disclosed in Japanese Patent Application Laid-open No. 62-297912, for example. In the prior art, a high-thermal fluid heated by a heater and a low-thermal fluid cooled by a cooler are mixed by means of a high-temperature flow regulating value and a low-temperature flow regulating valve, respectively, and this mixed fluid is circulated and supplied to an object whose temperature is to be controlled.
By means of this prior art, it is possible to adjust the temperature of a thermal fluid supplied to an object whose temperature is to be controlled, by adjusting the respective degrees of opening of the high-temperature flow regulating valve and the low-temperature flow regulating valve.
In systems, such as the prior art described above, wherein the temperature of a thermal fluid supplied to an object whose temperature is to be controlled is adjusted simply by controlling the respective degrees of opening of flow regulating valves, there is a risk that situations may arise where the thermal fluid cannot be controlled to a desired temperature due to reasons such as the following.
(1) Limits of performance resolution of flow regulating valves
In other words, the flow-rate of the thermal fluid passing through a flow regulating valve does not necessarily correspond to the degree of opening of the valve; for instance, there is a large out-flow of thermal fluid even when the valve opening is increased only slightly.
(2) Presence of hysteresis
In other words, in a case where the opening has changed from a small opening to a large opening and a case where it has changed from a large opening to a small opening, then even if the resulting degree of opening of the flow regulating valve is the same, there will be a disparity between the two cases in the flow-rate of thermal fluid passing through the flow regulating valve.
(3) Effects of pressure
In other words, when pressure fluctuations arise due to the circulating and supplying pump, then differences will arise in the flow-rate of the thermal fluid passing through the flow regulating valve, even in a state where the flow regulating valve is maintained at the same degree of opening.
In cases of this kind, the combination ratio between the thermal fluid passing through the high-temperature flow regulating valve and the thermal fluid passing through the low-temperature flow regulating valve fluctuates, and hence it is difficult to control the thermal fluid supplied to the temperature-controlled object to a prescribed temperature.
Moreover, in the prior art described above, since the temperature of the thermal fluid is controlled by adjusting the degree of opening of both flow regulating valves, then both flow regulating valves are operating constantly, which is very disadvantageous from the viewpoint of durability, in that it brings about early wearing, and the like.